Currently communication networks such as optical backbone networks are mainly based on OTN transport networks which typically follow a standard defined by ITU-T G.709/G.798. This allows the transport of many kinds of traffic using a variety of technologies (e.g Ethernet, SDH, etc). Inside the OTN network the traffic can be protected against faults using standard ODUk SNC protection as defined by ITU-T G.873.1. In particular, single homed CE client traffic transported inside the OTN network scenario can be addressed by ITU-T G.873.1
For instance, client side, the links to the edge node can be protected by MSP protection on SDH interfaces or by a LAG protocol on Ethernet interfaces. On the OTN side, where there are dual OTUk uplinks to other OTN nodes, the protection can be realized using ODUk SNC/I (i.e SNC Inherent) as defined by ITU-T G.873.1.
Another single homed scenario can be envisaged where there are separate links from the edge node to multiple other OTN nodes. At the client side the links can be protected by MSP protection on SDH interfaces or by LAG protocol on Ethernet interfaces as for the previous example. On the OTN side, the protection can be realized using ODUk SNC/N as defined by ITU-T G.873.1
The existing OTN protection mechanisms however cannot address a dual homed CE scenario. Protection schemes are generally arranged to compensate for failures in a network by detecting failure of one of the nodes, or inter-node connections, in the network, and re-routing traffic to bypass the failure. Networks generally have a number of edge nodes at which traffic can enter and leave the network, and a number of intermediate nodes through which traffic can pass to travel from any one edge node to any other. Customer equipment that is arranged to communicate over the network will generally communicate with one or more edge nodes. In a single homed scenario, the customer equipment can only communicate with one edge node which operates as the ingress node. Therefore any re-routing carried out by the protection scheme cannot bypass the ingress node at which traffic enters the network, or the egress node at which it leaves the network.
Dual homed schemes are known in which the customer equipment can communicate with more than one ingress or egress node. This provides resiliency so that if one of the edge nodes suffers a failure, then the customer equipment can still communicate over the network. However such dual homed schemes are not compatible with the existing OTN protection schemes, which have no way of handling a change in ingress or egress node.